Condition control apparatus with multipoint calibration



Aug. 7, 1951 A. B. "CHUDYK 2,552,890

' CONDITION CONTROL APPARATUS WITH MULTIPOINT CALIBRATION Filed Jan. 26, 1948 I IINPL/FIE/T Patented Aug. 7, 1951 CONDITION CONTROL APPARATUS WITH MULTIPOINT CALIBRATION Alex B. Chudyk, St. Louis Park, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application January 26, 1948, Serial No. 4,285

11 Claims.

. 1 This invention relates generally to improvements in intake manifold pressure control systems for engines that may be of the internal combustion type, and more particularly with im--- provements in the calibration of the control system controlling the intake manifold pressure for such engines.

In present day aircraft of the type adapted for flying at high altitudes, it is customary to employ the exhaust gases from the engine to drive a turbine driven air compressor to maintain high powers from the engine at high altitudes. 7 Controlling the volume of aircompressed by sucha compressor is a waste gate or valve which is vari-' ably positioned by an electrical network in accordance'with the demand for pressure at some particular point on the intake of the engine. The electrical network generally employed in positioning the waste gate of the compressor control usually consists of manual selecting means, a

calibrating network, a pressure sensing device; a turbine overspeed. limit device, and a position' compressors, it has been customary to provide a calibrating device which insures that the pressure maintained by the compressor is one particular value for a certain setting of the manual selector. This type of calibration would be sufficient if the relationship between movements of the manual slider and the resultant change in flow of air from the compressor was a linear relation. This, however, is not true for when the waste gate makes a linear movement, the flow of exhaust gases past the waste gate is not linear which results in anon-linear flow of air from the compressor.

The present apparatus is concerned with an arrangement for calibrating the electrical control" network to give a desired flow of air from the compressor at the two extreme positions of operation of the apparatus. By providing such an,

arrangement it is possible to more nearly be assured that all operating points between the twocalibrated positions are approaching the desired operating condition. 1 .It is therefore an object of the present invention to provide in a condition controlling appa ratus a calibration network which 'iixes the 2 calibration of two points in the operating range of the control apparatus.

A further object of the present invention is to provide in a condition controlling apparatus a calibration network which fixes the calibration of two points in'the operating range of the control apparatus and causes the control condition to approach the desired value at all points between the two calibrated points.

A still further object of the present invention is to provide in a condition controlling apparatus a calibration network operatively interconnected with a manual selector to variably adjust the calibration of said control apparatus in accordance with the position of the manual selector.

Still another object of the present invention is to provide an electrical network having therein a pair of electrical circuits interconnected by variable coupling means so that the network will have on its output terminals a signal representative of the sum of the circuits when the coupling means is in one position and a signal representative of one of the circuits when the coupling means is in a second position.

These and other more detailed and specific ob-' jects will be disclosed in the course of the following specification, reference being had to the accompanying drawing on which is a diagrammatical showing of a complete engine, induction and exhaust system with a turbo supercharger, and my invention applied to the control system thereof.

Referring to the single figure, the numeral!!! represents an aircraft engine of the radial type which is connected through a drive shaft to a propeller hub II to which are attached a plurality of propellers l2. Air for the engine In is taken in through a conduit l3 and is compressed by a centrifugal compressor M which forces the compressed air through a conduit IS, an intercooler I 6, and a conduit I! to a carburetor It. The air in the carburetor I8 is mixed withappro priate fuel and is fed through a further conduit is to a direct driven compressor 20. The compressor 20 forces the air and fuel mixture into the intake manifold 21 of the engine Ill. An exhaust manifold 22 carries the exhaust gases from the engine I!) away from the cylinders through a conduit 23 which in turn carries the gases to an exhaust driven gas turbine 24. The exhaust turbine 24 is coupled to the centrifugal compressor l4 through coupling 25. Controlling the amount of exhaust gas that will flow through the turbine 24 is a waste gate valve 25 which serves to con-' trol the by-passing of exhaust gases around the output of the electrical network is fed through-3 an amplifier 80 which in turncontrols the ener:

gization of the waste gate motor 21, as-will be explained hereinafter. The amplifier 8flis of the type adapted to amplify alternating current of a frequency corresponding to the 'frequencybf' the power source. The phase "or the output voltage of the amplifier signal is determinedby the phase of the signal voltage on the input terminals of the amplifier. The waste gate motor 21' is of the two-phase reversible type and therefore it;is-possible. to drive; the motor in one'direction or the other in accordance with the phase-of the. signalson the energizing-windings of the motor.

Theanetwork35 consists oii'a transformer 36 having-a priinary windingrfl energized' iroin' a common source of power, and a secondaryiwinding 38,; having-taps at 33 and 40. Connected across; the ends-of the secondary 38 is apetem tiometer 4| having a slider which is. actually the:1nanual selector for the control network.. The slider 42' is grounded at 43. Also energizedaby: secondary winding 381s. a, calibration potentioms eter 44 i having a 'variabletap45f; Connected-.be tween .tap'dc of the secondary dfi'andthesiider; 45 of the-potentiometer 44- is a fader potentiom eter 46;having a slider 41 'mechanicallyconnected tol manual selector-42 by any suitable coupling meansAB so that. movement of selector 42: will produce a" corresponding movement of slider 41.

Aiurther calibration transformeris transformer 4,3;liaving a primarywinding'liil energized by a common source of power and-a secondary winding'il tapped at 52. Energized by'the-secondary winding 5! is a potentiometer 53=-having a variable t'an 54; The network 60 maybe seen-toconsist of'a power transformer 51' having: aiprimary winding '62 connected to a common source of power, and a secondary winding 53 being tapped at'ifi ended Connected acrossthe ends'ofthe secondary is an overspeed potentiometer ha'vingaslide-wire resistor 56 and'a slider EL-the latter being positioned by an overspeed sensing device 68 acting through. a coupling 63. Resistor; 1B is a by-pass safety resistor to prevent their being an open circuit should the slider ii! accidentallyv open circuit with 1 its associated slide-wire. 65. Should an open circuit occur, the resistorwill havethe effect of shifting the balanceof the control network in a waste gate open-= ingdirection' in a manner more fully explained in my copending application Serial Number 754,227, filed June 12, 1947. Connected across the overspeed potentiometer between one end of the slider of the potentiometer is a pressure responsivepotentiometer network consisting of a slide-wire resistor H and a slider 12. The slider 12 is positioned by a pair of bellows Hand 14' acting through a bellowsstem (5 in accordance with the pressure sensed in the intake system of the engine it through the duct 16. The numeral ll-represents the slide-wire resistor of the follow up potentiometer of the control network and is energized by the secondary B3by its connection at taps .54 and 65. The slider 18, associated with the-slide:-wire 11; is positioned by the: rota"- 4 tion of the motor 21 acting through the gear train 28 and coupling 29.

The amplifier 80 has a pair of control signal input terminals 81 and B2. Terminals B3 and 84 are provided for connecting the amplifier to a common alternating current power source. The output terminals 85 and 85' serve'to energize the winding 31 associated with the motor 21. The winding 88 of motor 21 is energized directly from the input power line through a phase shifting condenser 89.

Operation In'consideringthe operation of the subject control apparatus-it is necessary to recognize that the control signal which is fed into the amplifier 8g i derived from a number of series connected electricalbridges. The first of these bridges is the manual control bridge located within network 35 and consists of the manual control slide-wire 4| connected across the secondary winding 38. The output terminals for this control bridge are slider. 42 and tap 39 and-withslider 42-electrically opposite the tap 39, there will be no output voltage across. the terminals of the bridge. The next bridge in the series of bridges. within network 35-- is the calibration bridge which consists of thecalibration slide-wire 44- connectedbetween the tap 39 and the right end of the secondary 38. The output terminals of this network are the'slider 45 and the tap onsecondary 3.8. When, the slider is electrically oppositethe tap4il, there will be no output voltage across this calibration brige.. If, however, the output is taken across the output terminals of the manual control bridge and: the calibration bridge, that is between slider- 4z andw slider 45, there will be a voltage that will be-equal. to thevoltage existing between tap. 39

and 40 assuming thattap 3.9 is the electrical-cen-- A further calibration bridge is provided by con-- necting the slide-wire 53 across thesecondary 5|.

The output-terminals of this bridge are. slider. 54v With the slider 54" and tap 52 on secondary 5|. electrically opposite the tap, 52, there will be no output voltage across this calibration bridge.

'Therefore, whenrthe: voltage across the-manual control bridge'and the first described calibration.

bridgeare added in series to that'existing across the last-described calibration bridge, with the slid-- ers positioned'as described, the voltage wilI be the sum of the voltages of each network plus .the volt-- age thatis representative of thedisplacement of the center of the first'calibrationbridge from the center of. the manual control bridge, onthe;

voltage between tap 39 andllll of secondary 38.

It will be noted that interconnecting the first and ometer is connected to the slider 54 of the second.

calibration bridge. When the slider 41 is in its extreme left hand position all of the voltage aris- 1 ing from the first calibration bridge is added to that of the second calibration bridge While. when the slider 41 is in its extreme righthand position the voltage on the first calibrationnetwork will be bypassed since the slider 4T will be connected; directly to the tap40- by conductor I03. The

movement of the slider 41 will not'have any effeet on any voltage arising from the manual control bridge since the slide-wire 46 is connected acrossonly the output terminals of the first calibration bridge. From this it can be seen that with the respective sliders positioned as described the output voltage of network 35 will be slightly positive.

The network 60 also consists of a number of series connected bridges, the first of which is the pressure responsive bridge which consists of slidewire H connected across the ends of secondary 63. Actually the right end of slide-wire ii is connected to the right end of the secondary 63 through the overspeed slider 61 and normally the right end of slide-wire 65. The functioning of this latter will be explained hereinafter. The output terminals of the pressure responsive bridge are the slider 12 and the electrical center of the secondary 63. With slider 12 electrically opposite the electrical center of secondary 53, there will be no output voltage from the pressure responsive bridge. A further bridge in network 60 is the follow up bridge which consists of slide wire i1 connected to taps 34 and 65 on the secondary winding 63. The output terminals of this bridge are slider '18 and the electrical center between the taps B4 and 65, and with the slider directly opposite the electric center between the tap the follow up bridge will be balanced. The electrical center between the taps is actually selected to be to the left of the electrical center of the secondary 63 so that with both the pressure responsive bridge and the follow up bridge balanced, there will still be a voltage across the network E!) which will be equal to the voltage displacement between the secondary 63 electrical center and the electrical center between the taps 64 and 65. This voltage when measured between slider 12 and slider 18 with the polarity of secondary 63 as shown, with the left end negative and the right end positive, will be slightly negative.

The slightly positive voltage from network 35 when added to the slightly negative voltage from network 60 will equal zero volts assuming all of the respective sliders are in their balanced posi-' tions on their respective slide-wires since networks 35 and 60 are electrically connected in series by the conductor IUD. The output terminals of the series connected control network are slider 42 and slider 58. The slider 42 is connected to the'amplifier input terminal 82 by way of ground conductor 43 while slider 18 is connected to terminal. 8! of amplifier 8G by way of conductor ml.

With no output on the output terminals of the electrical control network there will be no input on the input terminals 8| and 82 of the amplifier 80. With no input on the input terminals of the amplifier 80 there will be no output signal. fed to the motor winding 8'! and therefore the motor 21 will remain stationary.

The amplifier 88 is of the type adapted to amplify alternating current of a frequency corre sponding to the common power source and this amplifier will amplify the input signal from the control network and energize the winding 81. The phase of the voltage applied to the wind ing 81 will be either in phase or 180 out of phase with the input line voltage while the voltage applied to the winding 88 will be 90 displaced from the input line voltage. From this it may be seen that when there is a signal being amplifiedby the amplifier 80 both of the windings Bl and 88 will'be energized so that the voltage on winding 31 will be leading or lagging the voltage on wind,-

ing 88 by electrical degrees depending on the phase of the signal on the amplifier input Such an arrangement as this makes it possible to have two directional rotation of the motor 21.

Assume now that there is a pressure decrease in the carburetor intake manifold I! which, for example, may be due to the plane carrying the subject apparatus to a higher altitude. This decrease in pressure would be sensed through conduit 16 by the bellows networks 13 and 14 which would in turn move the coupling link 15 and the slider 12. The slider i2 will be moved toward the right and such movement will unbalance the main control network so that there will be a negative voltage on the output terminals of the control network. With the negative voltage on the input terminals of the amplifier 88 there will be a rotation of the motor 2'! in such a direction as to introduce a more positive voltage in the network Bll. This positive voltage will be introduced by the movement of the follow up slider 18 which is positioned by motor 2'! acting through gear train 28 and coupling 29 and this movement will" be toward the right. When the slider 18 is moved to a new position the waste gate 25 is also moved to a new position which will. result in changing the speed of the compressor and the volume of the air compressed. This change in volume of air compressed will be sensed by the bellows 14 which in turn will move the slider 12 in a more positive voltage direction or to the right. With slider 12 moved toward the right in a pressure satisfied direction, the network will be unbalanced in the opposite direction and the waste gate motor will in turn be moved back toward the right to the balanced position.

direction to position slider l3 toward the right to balance out the unbalance created by movement of the manual slider. As the waste gate 26 is positioned at the same time as the slider 18,

there will be a change in the speed of the compressor and a resultant change in carburetor induction pressure. This change will move the slider 12 toward the left by an amount that willchange the voltage existing across the pressure responsive bridge so that when added to that existing across the follow up bridge the sum will equal the unbalance created by movement of the manual slider 42. From this it can be seen that the pressure selected by the positioning of the manual selector 42 is obtained by the subsequent movement of the waste gate 25 to a position which will result in the driving of compressor 14 at a predetermined speed and that the pressure sensing bellows will maintain the selected pressure at a desired value.

For safety purposes, an overspeed controller 68 is provided to prevent the turbine 24 and the compressor Hi from exceeding a maximum safe rotational speed. Upon the occurrence of an overspeed of the turbine driven compressor the overspeed controller 68 will function to move the slider 61 toward the left across its associated slide-wire 66. The movement of the slider 61 toward the left has the effect upon the control- Thus the waste gate is adjusted to regulate the speed of the com-' aseasec:

network to. reduce the controlling, effect of the pressure responsive potentiometer. Hand slider.

12 and to shift the. balance point of the control network. in a waste gate opening direction. In

' other'words, the movement of the slider 51 towardthe left will cause thereto be a less negative voltage to exist across the control network '60 which will besensed by the amplifier 80, the latter of which will drivethe motor 2? in a direction to open the waste. gate 26 and reposition the slider 'lflto bring balance to the electrical network.

With wastegate 25 moved in an open directionthespeed of the turbine will decrease.

Asyet, no consideration has been given to the.

calibration network associated with the present control apparatus. A. calibration networkis providedjv in a proportioning system such as the type shown and is required to secure the proper relationbetween themeans for selecting the pressure.

to be controlled and theactual pressure that will bemaintained. In other words, it is desirable. for eachposition of .themanual selector 42 that there be a particular pressure maintained within the intake system of the engine 10; If the relation betweenthe movement of the slider 42 or slider '18; and the resultant. changes in volumes of air compressed by the compressor 1 l4 assuming the desired. ratio between control signal and waste gate; movement exists were a linear relation it wouldbe-necessaryto' calibrate the control system at only one point. and thus any other movement-of the: slider 42 would result in. a pressure that would. be desired for the movement made.

Since, however, the relation'between the move- The operationofmy calibration network may best; be understood. by considering how the entirepcontrol network is calibrated. With the system in operation, the manual control slider 42 is moved. to the extreme left position or toth'e minimum pressureposition; When the slider 42 is in the left position, the slider. 47 of the fader potentiometer is movedzto its extreme right position'since it is interconnected by suitable coupling means48 to the slider. 42. With the sliders 42 and 41 positioned as above, the control signal for thenetwork'35 may be traced from the ground terminal 43 throughslider 42, the manual control bridge, secondary tap 39 to tap 40, conductor I03, slider 41, conductor I04, slider 54, the second calibration. bridge to center tap 52 of'secondary 5| and. the conductor I00. In reviewin the last tracedcircuit innetwork 35'it will be noted that the only network which may be adjusted to affect the controlling voltage of the network 35 will be the second calibration bridge and its associated slider 54. It will be noted that the first calibration network is completely bypassed by conductor I03. The second calibration network will then be used to'select the pressure desired for the minimum position of theslider 42. To arrive at the. second point of calibration of the control network, it is necessary to move the slider 42 to theextreme-right hand position or to the'maxie mum; pressure position. When the. slider 42 is:

in the right handpositionthe slider 41 oi. the fader potentiometer willbe'moved to its extreme left hand position; With the control slider in thelast mentioned position, it may be seen' that the output. voltage in the-network 35 may be traced from the ground terminal 43, slider 42,.slide-wire: 44, tap 45, slider 41, conductor I04, tap 54, slide wire 53, secondary 5| to tap 52 and conductor I00. This. last traced circuit may be seen to'includezthe slide-wire resistor 44 and the slider 45.- which may be. considered as the maximum pres-- sure calibrationpotentiometer. To obtain thede sired pressure for themaximumposition. of the slider 42 the tap 45 of. the maximum. pressure calibration potentiometer is-moved until the. desired'pressure setting is reached.

It-ma-y now be seen that the control network is: calibratedfor the minimum pressure positionof' slider 42 anda maximum pressure position of the slider 42. By providing a fader potentiometer; connected directly across the maximum pressure calibration potentiometer, it is 'possibleto vari ably adjust the calibration of the control networkasthe manualcontrol slider 42- is moved between: th maximum and minimum pressure positions. This-'is accomplished by the movement of theslider 41 which may be seen to variably select the amount of signal. tobe taken from the maximum pressure calibration network as the slider is moved from: either ofits'two end ositions.

From the above, it may be seen that a pressurecontrol apparatus having a non-linear. control effeet-has. been provided wherein the apparatus may be calibrated at two end positions of operation: to better maintain thepressureat the de.-: sired .value.. Further, I a controlv apparatus has. been provided wherein it is possible to have a fixedamount of a control condition at afirst position of the control apparatus and. a second amount of a control condition and at a second position of the control apparatus and providing therewith a selector to variably adjust the value of calibration betweenthe first and second positions as the condition is-variably selected.

Although I have described my invention in connection with a pressure control. apparatus for an internal combustion engine, and while it is particularly well adapted foruse there, it will beobvious to thosev skilled in the art that my inventicn could be applied to any apparatuswhere it desirable to provide two point calibration with variable calibration between the two points? Therefore, I intend to be limited solely by the scope of the appended claims, in which I claim:

I claim as'my'invention:

1. In a condition controlling apparatus, a motor for positioning a condition regulating device; motorcontrol means including a device respon'- sive to a c'ontrollingcondition for positioning said motor in accordance with the value of said condition, condition selecting means associated with said condition responsive means and comprising an adjustable element, said condition selecting means being' effective when said adjustable element is moved to vary the position of' the motor which is maintained by said motor control means,- first "and second calibration means associated with said condition selecting means for varying'the position of the motor assumed for a given position of said adjustable element, and means controlled by said adjustable-element for causing the position of said motor to be controlled by only said first calibration means when said adjustable ele menti's at'oneend of its range of movement and by both said. first andsecond calibration means when said adjustable element is at the-other end of its range of movement so that it is possible to independently adjust the positions of said motor assumed when said adjusting-member is at the opposite ends of its range of movement.

2. In a controlling apparatus for regulating the magnitude of a condition; condition regulating means being operative to regulate a condition; manual means for selecting the magnitude of the condition to be regulated; condition sensing means for sensing the magnitude of the condition; calibration means having an adjustment independent of said manual means for determining the relation between the magnitude of the condition selected by said manual means and the condition regulated by said regulating means; acomplex balanceable electrical network having the individual adjustable impedance branches there! of common to each of said regulating means, said manual means, said calibration means and said sensing means; amplifier means connected to said network, said amplifier being operable to position said condition regulating means in accord,- ance with the unbalance of said network; and coupling means interconnecting said manual selecting means and said calibration means to variably adjust the relation between the magnitude of the condition selected by said manual means and the condition regulated by said regulating means as said manual means is adjusted.

3. Condition controlling apparatus, said apparatus comprising manual means for selecting the magnitude of a condition, sensing means for sensing the magnitude of the condition selected by said manual means, condition regulating 1 means for regulating the'magnitude of a condition, calibration means fortdetermining the relation between the position of said manual means and the magnitude of the condition regulated by said regulating means, separate adjusting means 1 for each calibrating means, electrical means operably interconnecting said manual means and said regulating means so that said manual means is operable to position said regulating means, electrical 'means interconnecting said sensing means and said regulating means so that said sensing means will maintain said regulating means in a position to maintain the condition selected by said manual means, and coupling means interconnecting said calibration means and said manual means so that the said calibration means is operable to vary the controlling eilect of said manual means on said regulating means as said manual means is adjusted.

4. In a condition controlling network being operable to maintain a condition, condition selecting means for variably selecting the magnitude of a condition to be maintained, and calibration means for adjusting the relation between the position of said condition selecting means and the magnitude of the condition to be controlled, said calibration means comprising a first resistance calibration network having an adjustment independent of said selecting means, a second resistance calibration network having an adjustment independent of said selecting means, means variably interconnecting said first and second networks and said condition selecting means of said controlling network to variably adjust the calibration of said controlling network in accordance with the positioning of said condition selecting means.

5. An electrical network comprising in combination, first and second alternating current power sources, a tap on each of said power sources, first 10 and second potentiometers each having a variable tap, means interconnecting said first power source and said first potentiometer and said second power source and said second potentiometer to comprise first and second electrical circuits respectively, said circuits each having output terminals in the taps of saidpotentiometers and said power sources and having thereon alternating current phase and voltages determined by the positions oi -the taps of said potentiometers, a third potentiometer having a variable tap, means connecting said third potentiometer across the output terminals ofthe first of said electrical circuits, means connecting the tap of said third potentiometer to one of the output terminals of said second electrical circuit, network output terminals comprising the other of the output terminals of said second electrical circuit and either of the output terminals of said first electrical circuit, said network terminals having an output voltage thereonequal to the sum of the voltages of said first and second electrical circuits when the tap of said third potentiometer is in one position and equal to the voltage of said second electrical circuit when the tap of said third potentiometer'is in a second position.

6. In a condition controlling apparatus, .a motor for positioning av condition regulating device, a balanceable electrical network, means comiecting said network to said motorso that said motor is operative to rebalance said network whenever said network is unbalanced and regulate a condition in accordance with the balance point of said network, electrical means for vary-'- ing the balance of. said network, said means comprising manually operated selecting means movable. over arange of values, first and second calibration means having adjusting means independent of said selecting means for determining the relation between the position of said selecting means and the magnitude of a controlled condition, and means interconnecting said first and second calibration means with said selecting means so that the balance point of said network is determined by said selecting means and said first calibration means when said selecting means is in one extreme position and by said selecting means and said first and second calibration means when said selecting means is in the other extreme position.

'7. In a condition controlling apparatus, an electrical balanceable network whose point of balance is a measure of the magnitude of a controlled condition, and means for varying the balance point of said network, said means comprising a manually operated condition selecting means movable over a range of values, first and second calibrating means having adjusting means independent of said selecting means whose adjustment varies the relation between the position of said selecting means and the magnitude of a controlled condition, and means interconnecting said first and second calibration means with said selecting means so that when said selecting means is in one extreme position the point of balance of said network will be determined by said selecting means and said first calibration means and when said selecting means is in the other extreme position the balance point of said network will be determined by said selecting means and said first and second calibration means.

8. In a condition controlling apparatus, an electrical balanceable network whose point of wee eens ion, nd

ane hdnt o sa d in a fi s 'r r dee ha in a m nua adiu te "fo t e ala ce of sa dbr dee, first s e- Qns e l h i tion br d es o determini the relation between the pos tion .oi th manual .adinstor or sai fi st rid e a d the ma ni ude of the 1col tro ed condit on. and electrical mea i t m et n sai first andseeond calibration vbri s and the manilaladiustoror said first bridge so that. the balance point ofsaid network will be deter-mined by ithehalance of said first bridge and said first calibration bridge when said ad! duster is in one .position and by the balance of said first bridge and said first'and second cali- Joration bridges when said adjustor is in a second position. a

--9. In a .eondition controlling apparatus, a motor for positioning a condition regulating deviqe, a balanceable eiectr-ieal network, -means connecting said network to said motor so'that said motor is operative to iiebalanee said network whenever said network isunbalaneed, manually operated electrical-means for varying the baianee of said network .to select a value of a controlled eondi-tion, aplurality of manually adjusted calibration means for determining the relation between unbalance of said'network and the desired yaiue .of the control condition as selected -by said manually operatedmeans, aeaeh ofsaid calibration means having an adjustment which is independent of said manually operated means, nd me anica means interconnecting said manually Qperated means and said calibrationv means so that theefiectof saidcal-ibration means s. va iably adjusted upon movement ofsaid man.- ually operated means.

, I 0.. aeenditiqn networkf nanua y opera ed-eqndit en seleet neme ns, a plurality of 'rnanuall-y adii s ed cal bra in Pier in pendently sel etin the elationbe weenth Position of said sele tinameans and fill d/@1 11? re 1a i ontrolsconditionet a pli -aii-typoi pos tions of said-sele t n means, and means fmtemonne t n said .ealibratin -zneansam said s eeting means to variably adj-11st the effect of said calibratin meansonsaid network as said selectingmeans. is adjusted to varyathe relation between the position of-said selectin means and the controlled condition. V. 1 v

--1-1.-I-n a,c 0ndition controlling network, +an adjustablemanuallyzeperated condition selecting means movable over a predetermined range,-a plurality of manually adjusted calibrating means, each of said calibrating means having an adjustment independent of said selecting means and eachefiec-tive to adjust the relation between the magnitude of the oontrelledicondition with re speet to the-position of the selecting means at different adjustmentsof said selecting means on said range, and means interconnecting said seieetingmeans and said'calibrating means so thatas said seieoti-ng means is' moved over said range each of said ealibrating means will be effective at said difierent adjustments.

7 ALEX B. CI-IUDYK.

,7 -REFEBENGES-CITED The'followin'greferenoes are of record in the Number Name v -Date 2,173,331 iiaines Sept. 19, 1939 

